This application is based on Application No. 2001-148843, filed in Japan on May 18, 2001, the contents of which are hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a power steering system which computes an error in the reading of a detected torque value of an interface circuit of a torque detecting portion by means of a controller for controlling an electric power steering control unit and which makes it possible to effect correction for restraining error on a software basis.
2. Description of the Related Art
A conventional power steering system will be described with reference to the drawings. FIG. 5 is a diagram showing the system configuration of a conventional power steering system.
In FIG. 5, numeral 1 indicates an external device, and numeral 2 indicates an electric power steering control device. Numeral 3 indicates a controller, numeral 4 indicates a torque sensor, and numeral 5 indicates a motor.
Further, in the drawing, numeral 11 indicates a condition setting portion, numeral 21 indicates a detecting portion, numeral 91 indicates a torque sensor adjusting circuit portion, and numeral 24 indicates a control portion.
Next, the operation of the conventional power steering system will be described with reference to the drawings.
In a conventional method for restraining torque value reading error, the precision of the parts used in the detecting portion 21 of the controller 3 is controlled to thereby control the controller 3 so as to involve as few errors as possible.
Further, to achieve an improvement in accuracy, an arbitrary torque signal is input from the external device 1, and a detection torque signal of the controller 3 is measured. To eliminate the error involved, correction is performed on a hardware basis by soldering an adjusting resistor, etc. to the torque sensor adjusting circuit portion 91.
That is, conventionally, the correction of the detection value of the torque sensor 4 is performed as follows. The external device 1 and the controller 3 are connected to each other. An arbitrary torque signal is input from the external device 1, and the torque signal used by the controller 3 is measured. To cancel the differential therebetween, correction for eliminating reading errors is performed on a hardware basis by an adjusting resistor, etc. of the torque sensor adjusting circuit portion 91.
By thus performing correction on the controller 3 on a hardware basis, the torque signal detected by the controller 3 is taken in by the control portion 24 as a normal value, making it possible to perform control.
The conventional power steering system described above has a problem in that when correcting a reading error of the torque sensor 4, which cannot be corrected even by part precision control, it is necessary to perform the correction from outside or provide a reference value for the torque sensor 4, so that dedicated equipment is required, resulting in rather high cost. Further, in effecting correction, it is necessary to perform a hardware operation such as the mounting of an adjusting resistor, etc.
This invention has been made with a view toward solving the above problem in the prior art. It is accordingly an object of this invention to provide a power steering system in which the correction of the detection torque value is effected not from outside by means of an adjusting resistor or the like but on a software basis, whereby it is possible to cancel the torque-detection interface reading error of the controller itself.
In accordance with the present invention, there is provided a power steering system comprising an external device for outputting an arbitrary torque signal in an error measurement mode, and an electric power steering control device which detects the torque signal, computes the differential between the detected torque value and a reference torque value, stores the differential as a torque correction value, and uses the detected torque value after correcting it by the torque correction value in the actual control mode.
Further, in accordance with the present invention, the external device includes a storage instruction portion for giving instructions to operate in the measurement mode and a condition setting portion for outputting the arbitrary torque signal, and the electric power steering control device includes a torque sensor for detecting a steering torque applied to the steering system of the vehicle, a motor for generating a steering assistance torque in accordance with a control current, and a controller having a detecting portion for detecting the torque signal through the torque sensor, a computing portion for computing the differential between the detected torque value and a reference torque value, a storage portion for storing the differential as a torque correction value, and a control portion which, in the actual control mode, corrects the torque value detected by the torque sensor by the torque correction value and outputs a control current for the motor in accordance with the corrected torque value.
In accordance with this invention, there are provided a power steering system comprising an external device which, in an error measurement mode, outputs an arbitrary torque signal, computes the differential between the transmitted detection torque value and a reference torque value, and sends out the differential as a torque correction value, and an electric power steering control device which detects the torque signal, transmits the detected torque value to the external device, stores the torque correction value transmitted from the external device, and, in the actual control mode, uses the detected torque value after correcting it by the torque correction value.
Further, in accordance with this invention, the external device includes a first communicating portion which gives instructions to operate in the measurement mode, receives the detected torque value, and sends out the torque correction value, and a condition setting portion for outputting the arbitrary torque signal, and the electric power steering control device includes a torque sensor for detecting a steering torque applied to the steering system of the vehicle, a motor for generating a steering assistance torque in accordance with a control current, and a controller having a detecting portion for detecting the torque signal through the torque sensor, a second communicating portion for transmitting the detected torque value to the external device and receiving the torque correction value, a storage portion for storing the received torque correction value, and a control portion which, in the actual control mode, corrects the torque value detected by the torque sensor by the torque correction value and outputs a control current for the motor on the basis of the corrected torque value.
Further, in this invention, the first communicating portion of the external device and the second communicating portion of the controller are connected to each other in a wireless fashion.
Furthermore, in this invention, the torque correction value is a gain correction value of the torque signal.